Swetha

This is a good question. In short, no, every feature doesn't require a PM to specifically oversee it all the way through the cycle.

A good development team and an engaged designer working with PM can work wonders. I've had that situation and building products in that culture is great.

As for "business value" of design, my first question would be to define what "business value" means. No one I've met actually defines business value in meaningful ways. It's usually from a cost or revenue perspective which is not a meaningful way. If we were to use the same metrics to measure HR or Finance, we could only conclude they should all be laid off.

Jared Spool has been a huge advocate about the value of design. I would look up his writing. I'm sure you'll find a lot of good info. e.g. https://www.linkedin.com/pulse/diagram-shows-value-great-ux-jared-spool-2rxae/